1. Field of the Invention
This invention relates generally to a method and unit for storing a radiation image, and more particularly to a method and unit for storing information on a measurement made on a radiation image which is displayed on the display screen of an image display unit, along with the radiation image.
2. Description of the Related Art
A computed radiographic (CR) system has recently been put to practical use to obtain radiation images ranging over a very wide radiation exposing area. In this CR system, the radiation-image information of a subject such as a human body is temporarily recorded on an accumulative fluorescent sheet. The accumulative fluorescent sheet accumulates part of the energy of radiation (X-rays, α-rays, β-rays, γ-rays, electron rays, ultraviolet rays, etc.) if the radiation is emitted, and emits accelerated fluorescent light in accordance with the accumulated energy if excitation light such as visible light is emitting, thereafter. The sheet with the image information recorded thereon is scanned by excitation light such as a laser light beam and is caused to emit accelerated fluorescent light corresponding to the image information which is signal light. The emitted fluorescent light is read by photoelectric reading means such as a photomultiplier, whereby an image signal is obtained. Based on this image signal, the radiation image of the subject is output as the visible image to a storage medium such as photosensitive material and to a display unit such as a cathode-ray tube (CRT) display unit (Japanese Unexamined Patent Publication Nos. 55(1980)-12429, 56(1981)-11395, and 56(1981)-11397).
For the accumulative fluorescent sheet that is employed in the CR system, half size, large-square size, quarter size, one-sixth size, etc., have been prepared according to the photographic object. Also, in order to record a lengthy subject as a single image, investigation has recently been carried out with respect to performing photographing and recording by employing two or more sheets of the existing sizes, such as half size, put side by side, or by employing a sheet longer than the existing sizes.
Incidentally, in orthopedic surgery and the like, among medical fields, the negative film from which a radiation image was output is employed not only for observation and photographing but also for the purposes of measuring scoliotic curvature (Cobb method and Ferguson method) and a kyphotic index. Measuring points are actually marked on the film from which a radiation image was output, and the distance, angle and the like between the marked measuring points are manually measured with a measuring tool such as a ruler, a protractor and the like. Based on the measured distance and the like, the aforementioned scoliotic curvature and the like are obtained by calculations.
Since, on the other hand, the radiation image obtained by the CR system is digital data as described above, measurements can be made automatically, by displaying the radiation image on the display screen of an image display unit, then specifying measuring points on this display screen, and storing a method of measurement in advance. Furthermore, if methods of calculation for the aforementioned scoliotic curvature and the like are stored, it will become possible to calculate these automatically and the measuring load of a measurer, such as a doctor, a radiation technician and the like, can be reduced appreciably.
In the above-mentioned orthopedic surgery and the like, incidentally, the same subject is again measured by photographing a radiation image in order to judge the course of the medical treatment, and the result of measurement is often compared with the previous result of measurement.
When making measurements on film, as described above, points on the present film corresponding to the pervious marked points are marked and measured, while the present film is being compared with the previous film on which the previous measurement was made.
However, when measurements are made based on the radiation image displayed on the display screen of the image display unit, as described above, it cannot accurately be grasped which point on the radiation image displayed on the display screen has been measured and what measurement result has been obtained. Particularly, when a doctor or a radiation technician making the present measurement differs from a doctor or the like who made the previous measurement, it is difficult to recognize the previous measuring points and measurement result and there is a problem that an accurate comparison between measurement results cannot be performed.